Respuesta :

4x+30=90
4x = 60
  x = 15

answer is B. 15
Since b and d are perpendicular the angles they form are 90 degree angles.  Also given that a and b are parallel the angles between a and d are the same as those with b and d.

SO we can say that 4x + 30 = 90
4x = 60
x = 15